The present invention relates generally to encoder reader testers and more particularly to a reader tester for reading message information generated by an encoder in a meter of an automatic meter reading system to test to see if the meter dial readings in the message from the encoder correspond to the actual dial readings on the face of the meter.
Systems for automatically reading residential electric, gas and water meters from a central location have come into commercial reality in the last few years. A basic automatic meter reading system consists of three parts or functions: an encoder mounted within a meter, a communication system, and a reading center. The encoder provides the means of converting a mechanical meter reading from a meter into a form suitable for communicating, via the communication system, to the reading control center. One of the prime requirements in this type of system is that the encoder meter information transmitted over the communication system be error free. The reason for this is because the automatic meter reading will be used to acquire data for billing the consumption of electrical energy, gas, water and the like. For years the established standard for accuracy and reliability in a utility meter has been in the meter at the consumer's residence or place of business. This standard is generally trusted by the consumer, the public utility and the public utility commission and the information displayed on the meter register or index of the meter is accepted as a true and accurate record of consumption. In order to obtain this established trust by consumers and the public utility commissions, the on-site visual display of consumption must ideally be retained. Secondly, in an automatic meter reading system, the automatic reading must agree with the visual display and there must be a high degree of assurance that the automatic meter reading will agree with the visual display without the need for actually confirming the automatic meter reading with periodic readings of the visual display.
It is recognized that it is not just enough to simply encode the meter reading and expect that the visual display and the automatic reading will always be the same--encoding equipment will malfunction, therefore there will be errors. Thus, what is required is an encoder reader and tester apparatus for supporting automatic meter reading systems which can detect for encoder errors and also detect for the valid operation of the encoder. One known meter capable of generating coded output information from an encoder is disclosed in U.S. Pat. No. 3,846,789 entitled "Remote Reading Register with Error Detecting Capability" assigned to the assignee of the present invention. In that patent, a novel remote reading register comprises an encoding mechanism which has the capability to resolve ambiguity in formulating an encoded message representative of the dial readings on the register indicators, and having in addition thereto, the capability of providing encoded information which may be utilized to detect the transmission of erroneous and non-erroneous encoded messages. Utilizing the data transmitted by the encoder of that patent, there is a high degree of assurance that an accepted reading at the remote location, such as a reading control center, is in fact precisely the same as would be a visual reading taken directly from the dial indicators on the face of the meter at the meter location.
In the aforementioned patent, it is disclosed that the meter reading information generated by the encoder register can be utilized to determine the decimal dial readings and further to check for encoding errors which are contained in the meter dial information transmitted by the encoder. A conventional decade mechanical gear train is utilized to drive a kilowatt-hour register comprised of five dials. Further, each shaft has a dial drive gear and also contains a slotted optical encoding disc which is rotatable by a motor to generate pulse code digital information representative of the decimal dial reading of each dial on the meter. The detection of errors is an encoder meter of the type disclosed in the aforementioned patent, is referred to therein as interdial checking and is based on the following principle: each gear in a mechanical gear train has a definite and positive mechanical relationship to the other gears in the train. If the angular position of one gear is known, other gears in the train are restricted to certain angular positions relative to the known gear. By establishing certain known angular positions of the relationships of the gears, it is possible to accurately determine the true dial reading of each dial by comparing the interdial readings between the gears in the meter encoder. It is recognized in this patent that the encoder information can be used for interdial checking of errors in the encoder message, however no known reader tester apparatus is known to exist for accurately testing the operation of encoders of the type disclosed. Therefore, a need exists for an encoder reader tester apparatus capable of interrogating a meter encoder and detecting errors in messages generated by the encoder.